ON A PEACH-COLOURED BACTERIUM. 31 



teria I am inclined to think that the former is not, on the 

 whole, a more sluggish form than are the colourless species. 

 In the gioeogenous condition all Bacteria are motionless, and 

 it is only the biscuit-shaped form of plastid or still more 

 elongated forms which exhibit " vital" movement. 



The question as to the mechanism of locomotion in the 

 Bacteria is one which I have not been able to assist in 

 solving by examination of active B. rubescens. A priori, I 

 suppose all biologists are inclined to adopt the view that the 

 motile plastid of Schizomycetes is provided with one or two 

 protoplasmic flagella. The evidence in favour of the exist- 

 ence of such flagella is very nearly as convincing as any that 

 could be obtained by the actual inspection of a filament 

 attached to the plastid. I confess that I have not been able 

 to see the flagella in any form of Schizomycetes which I have 

 studied for the purpose, but I think there is every reason 

 for admitting the truth of the recent observations of Messrs. 

 Dallinger and Drysdale on this point. 



New Transition-fo7'ms of Plastids and Aggregates. — It will 

 not be necessary for me to repeat, on the present occasion, 

 the enumeration of the various kinds of plastids presented by 

 B. 7'ubescens, and the various modes in which these plastids 

 unite to form aggregates, linear, globose, retiform, and tes- 

 selate. I shall, without any preface, draw attention to two 

 interesting forms which I have observed since 1873, refer- 

 ring to my previous paper for a general account of the forms 

 assumed by the species. 



Fig. 3, Plate III, represents a series of plastids from a 

 groAvth in which such forms constituted the greater part of 

 the sample. They may be described in the terminology 

 which I have adopted, as multilocular bacterioid plastids — 

 which occur in this case isolated — and free from a gelatinous 

 matrix. Those to the right hand side are interesting on 

 account of their elongation, furnishing, as they do, a transi- 

 tion-form to the filamentous plastids (leptothrix-form) 

 figured in vol. xiii of this Journal, Plate XXIII, figs. 

 24,25. 



Fig. 5 in Plate III is a small specimen of a form ot'B. rubes- 

 cens which is rare, and of very great beauty and interest. I had 

 only met with it on two occasions (one specimen being that 

 here figured) , when I received, in September last, from my 

 friend Mr. Archer, of Dublin, a gathering which contained 

 a great quantity of it, and very much larger aggregates of it 

 than that here figured. This form, which consists of strongly 

 marked unilocular bacterioid (biscuit-shaped) plastids (almost 

 like an hour-glass in shape), united with the greatest regu- 



